1. Field of the Invention
The present invention relates to an apparatus and a method for removing non-condensing gas in a heat pipe, and more particularly to an apparatus and a method for removing non-condensing gas in a heat pipe by pressure difference during degas process.
2. Description of Related Art
The heat pipes are suitable for heat dissipation of electronic device due to high thermal conductivity, fast thermal conductivity, light weight, fixed structure, simple structure and versatile usage. Moreover, the heat pipes can dissipate massive heat with no electrical power consumption. The conventional heat pipes are provided with wick structure on inner wall thereof and the wick structure is made of mesh with capillary function. By the capillary function, the working fluid in the heat pipe can be conveyed.
During fabrication of the heat pipe, vapor generated by heating is used to remove non-condensing gas previously present in the heat pipe. The method is applicable when the work fluid is liquid state in room temperature and is relatively not dangerous, such as water, Freon 113, and ethanol. The working fluid with excessive amount is firstly injected into the heat pipe and the vent hole of the heat pipe is temporarily sealed. Afterward, the heat pipe is heated such that the vapor pressure of the working fluid (for example, water) is 0.11-0.4 MPa, which is larger than the saturated pressure of the working fluid. The temporarily sealed vent hole is opened again to balance pressure inside and outside the heat pipe. At this time, the working fluid is rapidly vaporized and vapor is ejected from the vent hole. The ejected vapor will remove the non-condensing gas in the heat pipe. When suitable amount of non-condensing gas is removed from the heat pipe, the vent hole is sealed again to sufficiently degas the heat pipe. The amount of working fluid filled in the heat pipe should be calculated with reference to heating time, temperature and heat pipe shape to obtain the removing amount of non-condensing gas.
In above-mentioned method, the vapor is firstly confined by the sealed vent hole, the vent hole is not opened until the vapor pressure is sufficient to remove the non-condensing gas. However, the operation of repeatedly sealing the vent hole and then opening the vent hole will harden the opening provided by the vent hole, which may deteriorate the quality of heat pipe for future use.
Therefore, the conventional method for removing non-condensing gas still demands much improvement.